Hi Fi Corp not insuring that repairer fixes tablet

I took my Asus Fonepad 7 to the above mentioned Hi Fi Corp on 24.02.15. to be sent away for repair - there is dust under the screen ( top right corner)<br> The unit was sent to PartServe who kept it for 2 weeks. I collectted the unit from Hi Fi Corp on the 10.03.15 to find that it had been returned unrepaired , the dust ingress under the screen had not been removed.<br> The customer service department at Hi Fi Corp was unwilling to take the matter further , and see to it that PartServe rectifies the problem.<br> I have e.mailed PartServe twice and been ignored .<br> I would like Hi Fi Corp to see to it that my Asus Fonpad is repaired under warranty by PartServe.